I'm trying to write up a report on mendelian disorders. So I picked Thromobophilia. Thromobophilia is a multifactorial trait. According to OMIM (Online Mendelian Inheritance of Man),

"Thrombophilia is a complex (multifactorial) trait. The genes involved in complex traits are, for the most part, susceptibility genes, not genes that represent the primary cause of the disorder, as in the case of mendelian disorders. "